Sunday, April 12, 2015

Researchers Solve Young Sea Turtles' "Lost Years" Mystery

Kemp’s ridley sea turtles. Credit: Sea World

Juvenile sea turtles don’t just passively drift in ocean currents
during their “lost
years” as researchers once thought. Instead, turtles as young as 6-18 months of age are
very active swimmers, according to a recent study conducted by NOAA and the University of Central Florida. Researchers say that this revelation is an important new clue in the sea turtle “lost
years” mystery of where exactly turtles travel in their first years of
life before returning to coastal areas as adults to forage and
reproduce.

Upon hatching, young sea turtles swim offshore and disperse with the
help of ocean currents. The turtles are rarely observed by humans during the next
two to ten years. Previous studies suggested that at least some
juvenile turtles reside among mats of seaweedthat provide
shelter and habitat in the open sea. Not much was known about these
juveniles’ movements during this time (which is why researchers dub it the “lost
years”), but it had been widely assumed that turtles simply drift with
ocean currents.

To solve this mystery, researchers placed specially designed
solar-powered tags on 24 green & 20 Kemp’s ridley wild-caught sea
turtle toddlers in the Gulf of Mexico. The tags were tracked by
satellite for a short period of time before shedding cleanly from the
turtle shells (a maximum of 2-3 months). Next to the turtles, researchers deployed
small, carefully-weighted/passively-drifting surface buoys that were
also tracked by satellite.

When the drifter tracks were compared to the sea turtles’ movements,
the researchers found that the turtles’ paths differed significantly
from the passive drifters. Using observed and modeled ocean current
conditions, they found a difference of distance between the turtles and
drifters to be as much as 125 miles within the first few days. In nearly
every instance, the juvenile turtles’ swimming behavior appears to help them
reach or remain in favorable ocean habitats.

"The results of our study have huge implications for better
understanding early sea turtle survival and behavior, which may
ultimately lead to new and innovative ways to further protect these
imperiled animals,” said Dr. Kate Mansfield, director of the University of Central Florida’s Marine Turtle Research Group

“What is exciting is that this is the first study to
release drifters with small, wild-caught yearling or neonate sea turtles
in order to directly test the ‘passive drifter’ hypothesis in
these young turtles. Our data show that one hypothesis doesn’t, and
shouldn’t, fit all, and that even a small degree of swimming or active
orientation can make a huge difference in the dispersal of these young
animals.”